1. Field of the Invention
The present invention relates to a rotary atomizing electrostatic coating apparatus of the type capable of controlling a shaping air flow pattern.
2. Description of Related Art
Japanese Patent Publication No. HEI 7-24367 discloses a rotary atomizing electrostatic coating apparatus of the type capable of controlling a shaping air flow pattern. In the apparatus, as illustrated in FIGS. 8 and 9, shaping air nozzles 6' are arranged on a first circle having its circle center on an axis of rotation of a rotary atomizing head, and pattern control air nozzles 7' are arranged on a second circle having a larger diameter than the first circle. Each shaping air nozzle 6' has a nozzle axis inclined from a line parallel to an axis of the rotary atomizing head so that the shaping air flow pattern is spread in a direction away from the shaping air nozzles. The air expelled from the pattern control air nozzles 7' collides with the shaping air flow pattern and changes the pattern.
Since the shaping air is expelled from the nozzles at a high speed, the shaping air flow draws air around the flow to generate a secondary flow (accompanying air flow). It is important that the secondary flow freely accompany the shaping air flow without generating turbulence or a vortex so that a smooth shaping air flow is formed.
However, in the conventional apparatus, since the pattern control air nozzles are disposed radially outside the arrangement of the shaping air nozzles, free generation of the accompanying air flow is obstructed, producing a negative pressure adjacent the shaping air nozzles, causing vortices or turbulence V (FIG. 8) to be generated. As a result, atomized paint around the vortices is drawn to the region and in turn attaches to the atomizing head and the shaping air cap. Further, when the pattern control air is being expelled, the amount of the main air flow increases so that the negative pressure and the air turbulence are enhanced to draw more paint particles. The paint particles which adhere to the atomizing head and the air cap drop onto the body to be coated to degrade the coating quality.